The purpose of this project is to define the mechanism of regulation of the individual globin genes during erythroid differentiation. A previously constructed library of sheep genomic DNA fragments, cloned into E. coli using the bacteriophage vector - Charon 4A, was screened with probes specific for the beta-like globin genes of sheep. Four overlapping clones, the inserted fragments of which include 28 kb of sheep genomic DNA, were all found to contain a sheep gamma globin genes identified by DNA sequencing of the coding blocks. The gamma gene was compared to the previously isolated gene for beta a globin. Each gene contained two introns, one of 110 bp and the second of approximately 800 bp. Analysis of electron microscopy of heteroduplexes formed between recombinants containing either the gamma or beta A globin gene demonstrated that these genes are included in a 8 kb region of general sequence homology. Both the gamma and beta A genes were found to include moderately repetitive DNA sequences within their large introns. Several recombinants were identified which contain globin genes which on restriction endonuclease or DNA sequence analysis were identified as either encoding for embryonic beta-like globins or alternatively, these may represent pseudogenes, the function of which remains undefined.